In the production of oil and gas at offshore locations or in swampy areas, a pipeline is normally laid from producing wells to some kind of production collection facility. Quite often, subsequent production developments necessitate placing a branch line to intersect the pre-existing pipeline. As an example, the production line first installed may be a 12 inch pipeline. It may be necessary to install a lateral connecting line of up to ten inches in diameter. It is difficult in some circumstances and sometimes impossible to retrieve the pre-existent line, raise it to a dry position, cut out a portion of line and splice in a tee fitting. The present invention is a hot tap appartus which is adapted to be installed at the point of intersection. It enables the intersecting line to be connected to the pre-existing line without raising of the pre-existing line. The hot tap thus enables the connection to be achieved without interrupting operation of the line. As a consequence, the connective operation can be achieved in situ at the convenience of the service personnel.